The present disclosure relates generally to drilling systems and earth-boring drill bits for drilling a borehole through a subsurface formation, for example, for the ultimate recovery of oil, gas, and/or minerals. More particularly, the present disclosure relates to hybrid drill bits including fixed blades with cutter elements in combination with rotating cones with cutting elements.
An earth-boring drill bit is connected to the lower end of a drill string and is rotated by rotating the drill string from the surface, with a downhole motor, or by both. With weight-on-bit (WOB) applied, the rotating drill bit engages the subsurface formation and proceeds to form a borehole along a predetermined path toward a target zone.
In drilling operations, costs are generally proportional to the length of time it takes to drill the borehole to the desired depth and location. The time required to drill the well, in turn, is greatly affected by the number of times drill bits must be changed or added during drilling operations. This is the case because each time a drill bit is changed or added, the entire string of drill pipes, which may be miles long, must be retrieved from the borehole, section-by-section. Once the drill string has been retrieved and the tool changed or added, the drillstring must be constructed section-by-section and lowered back into the borehole. This process, known as a “trip” of the drill string, requires considerable time, effort, and expense. Since drilling costs are typically on the order of thousands of dollars per hour, it is desirable to reduce the number of times the drillstring must be tripped to complete the borehole.
During conventional drilling operations, it is often necessary to change or replace the drill bit disposed at the lower end of the drill string once it has become damaged, worn, out and/or its cutting effectiveness has sufficiently decreased. Regardless of the specific motivations, each time the drill bit is replaced or changed, a trip of the drillstring must be performed which thus increases the overall time and costs associated with drilling the subterranean wellbore.